In this situation, Chris should consider using a proprietary software license that includes restrictions on redistribution. Specifically, he can choose a license that allows users to use the software freely but prohibits them from redistributing it.
One common approach is to use a custom license agreement that explicitly states the terms of use, including the prohibition on redistribution. This allows Chris to retain control over the software while still providing it for free.
Alternatively, Chris could consider using an open-source license that includes specific clauses against redistribution, but such licenses are less common and may not align with the typical goals of open-source distribution.
In summary, a well-crafted proprietary license would be the best route for ensuring that users can access the software for free without the ability to redistribute it.